426 



ANATOMY FOR NURSES 



[Chap. XX 



BADIATING I 

 VESSELS 

 OF IBIS ' 





The ciliary body, — The ciHary body is located between the 

 clioroid and tlie iris, and contains the ciliary processes, and the 



ciliary muscle. Just behind 

 the edge of the cornea, the 

 choroid is folded inward and 

 arranged in radiating folds, 

 like a phiited ruffle, around 

 tlie lens. There are about 

 seventy of these folds, and 

 they constitute the ciliary 

 processes. They are well 

 supplied with nerves and 

 blood-vessels, and also support 

 a muscle, the ciliary muscle. 

 The fibres of this muscle 

 arise from the sclera near 

 the cornea, and extending 

 backward are inserted into 

 the outer surface of the ciliary 

 processes and the choroid. 

 The action of this muscle 

 determines the position of 

 the lens. 



Iris. — The iris (iris, rain- 

 bow) is a colored, fibro-muscu- 

 lar curtain hanging in front of 

 the lens and behind the cornea. 

 It is attached at its circumference to the ciliary processes, with 

 wliich it is practically continuous, and is also connected to the 

 sclera and cornea at the point where they join one another. 

 Except for this attachment at its circumference, it hangs free 

 in the interior of the eyeball. In the middle of the iris is a cir- 

 cular hole — the pupil — through which light is admitted into 

 the eye chamber. The iris, like the choroid, is composed of con- 

 nective tissue containing a large number of pigment cells and 

 numerous blood-vessels. It contains, in addition, two sets of mus- 

 cular fibres. One set is arranged like a sphincter with its fibres 

 encircling the pupil, and is called the contractor of the pupil. The 

 other set consists of fibres which radiate from the pupil to the 



Fig. 199. — Segment of the Iris, 

 Ciliary Body, and Choroid. Viewed 

 from the internal surface. (Gerrish.) 



